Indexing

ABSTRACT

Improvement in worktable apparatus having X and Y drive units for producing relative table-to-tool movements along perpendicular X and Y axes, respectively; the improvement consisting of indexing and cycling mechanisms for controlling table-to-tool movement and cycling of a tool unit, comprising a template having at least one physical characteristic varying along both the axes in accordance with the desired pattern of the movement and the cycling; first and second sensors, the template and the sensors being mounted to undergo relative sensor-totemplate movement in correspondence to the relative table-to-tool movement, the first sensor being responsive to a physical characteristic to provide table stop signals, the second sensor being responsive to a physical characteristic to provide table direction signals, one of the sensors being responsive to a physical characteristic to provide work cycle signals; and logic circuitry responsive to the sensors to cause the drive units to stop the relative movements in response to a table stop signal, to cause the tool unit to carry out the work cycle in response to a work cycle signal, and to cause the drive units to renew the relative movements in accordance with the table direction signals or hold the stop position in the absence of table direction signals.

United States Patent [191 Healy 1 INDEXING [75] lnventor: James W.Healy, Wakefield, Mass.

[73] Assignee: Cambridge Engineering Inc.,

Waltham, Mass.

221 Filed: Dec. 24, 1970 211 Appl.No.: 101,289

UNITED STATES PATENTS 3,232,142 2/1966 Deckl et a1. ....408/3 3,163,05712/1964 Drummond et a1. ..408/3 3,532,893 10/1970 Marantette et al...408/3 X Primary Examiner-Andrew R. Juhasz Assistant Examiner-Z. R.Bilinsky Attorney-Gordon R. Williamson [57] ABSTRACT Improvement inworktable apparatus having X and Y drive units for producing relativetable-to-tool move- 51 Jan.23,1973

ments along perpendicular X and Y axes, respectively; the improvementconsisting of indexing and cycling mechanisms for controllingtable-to-tool movement and cycling of a tool unit, comprising a templatehaving at least one physical characteristic varying along both the axesin accordance with the desired pattern of the movement and the cycling;first and second sensors, the template and the sensors being mounted toundergo relative sensor-to-template movement in correspondence to therelative table-to-tool movement, the first sensor being responsive to aphysical characteristic to provide table stop signals, the second sensorbeing responsive to a physical characteristic to provide table directionsignals, one of the sensors being responsive to a physicalcharacteristic to provide work cycle signals; and logic circuitryresponsive to the sensors to cause the drive units to stop the relativemovements in response to a table stop signal, to cause the tool unit tocarry out the work cycle in response to a work cycle signal, and tocause the drive units to renew the relative movements in accordance withthe table direction signals or hold the stop position in the absence oftable direction signals.

6 Claims, 8 Drawing Figures PATENTED JAN 23 I975 SHEET 1 BF 3PATENTEDJAN 23 1975 SHEET 2 UF 3 FIG 3 PAIENIEDJIIIIZB I975 3. 7 1 2.750sum 3 or 3 FIG 8 START I I b -I 2 I 2 O20- O2 O c 0 d SWITCH SWITCHSWITCH SWITCH I I I DIRECTION CONTROL MEMORY IRELAYS I SIZES I I I24dI24b I240 I34 ||Y|| XII LIGHT CLEAR SOURCE DRIVE DRIVE MEMORY UNIT I I Iv 54 1 7 80 L GATING PHOTOCELL UN'T I20 STOP CONTROL WORK l W] GATECYCLE T ING RELAY RELAYSI UNIT l32 L I28d I28b I280 TOOL CONTROL RELAY\I3O INDEXING This invention relates to indexing worktables.

Objects of the invention are to provide for highly accurate, automaticindexing in rapid response to program signals, and flexible, easilychanged programming, with apparatus having performance capability ofnumerical control but at lower cost, and in which any errors arenon-accumulating.

In general the invention features an improvement in worktable apparatushaving X and Y drive units for producing relative table-to-toolmovements along perpendicular X and Y axes, respectively; theimprovement consisting of indexing and cycling mechanisms forcontrolling table-to-tool movement and cycling of a tool unit,comprising a template having at least one physical characteristicvarying along both the axes in accordance with the desired pattern ofthe movement and the cycling; first and second sensors, the template andthe sensors being mounted to undergo relative sensor-to-templatemovement in correspondence to the relative table-to-tool movement, thefirst sensor being responsive to a physical characteristic to providetable stop signals, the second sensor being responsive to a physicalcharacteristic to provide table direction signals, one of the sensorsbeing responsive to a physical characteristic to provide work cyclesignals; and logic circuitry responsive to the sensors to cause thedrive units to stop the relative movements in response to a table stopsignal, to cause the tool unit to carry out the work cycle in responseto a work cycle signal, and to cause the drive units to renew therelative movements in accordance with the table direction signals ifpresent. In preferred embodiments the template characteristic .variesdiscontinuously along the axes, and the sensorsare respectivelyexclusively responsive to two such characteristics, which comprisetransmissivity of the template to light and air; the first sensor is aphotosensitive device; the second sensor is a pressuresensitive deviceconsisting of four pressure differential operated switches respectivelycorresponding to the four directions along the axes, and a pressurecontrol member having four exhaust openings respectively communicatingwith the switches and normally effectively sealed by the template; thetemplate has local areas of high light transmissivity, and local areasof high air transmissivity respectivelyextending from the areas of highlight transmissivity in the respective directions of desired renewal ofsaid relative movements, each area of high air transmissivity beingarranged to align with an exhaust opening upon alignment of thephotosensitive device with the corresponding area of high lighttransmissivity, there being selected additional areas of high airtransmissivity respectively extending from the areas of high lighttransmissivity in the trailing direction of the relative movement priorto the alignment, the logic circuitry being responsive to simultaneousair exhaustion through a pair of exhaust openings to cause the tool unitto carry out the work cycle; the template consists of a plate having arectangular grid of uniformly spaced holes, and a program mask forselectively exposing some of the holes and covering others; the secondsensor is responsive to a physical characteristic of the template toprovide the work cycle signals; the logic circuitry includes a memoryresponsive to a switch corresponding to an exhaust opening aligned withan area of high air transmissivity to prevent one of the selectedadditional areas of high air transmissivity adjacent a subsequent areaof high light transmissivity with which the photosensitive device isaligned from efi'ectively causing a switch to provide a table directionsignal; and table locking mating racks are provided for determining aseries of standard index positions for the table, and for correcting,after the table is stopped, any deviation of the table from the neareststandard position, the drive units being connected to the apparatusthrough compliant couplings to accommodate the correcting.

Other objects, advantages, and features of the invention will beapparent from the following description of a preferred embodimentthereof, taken together with the drawings in which:

FIG. I is a side elevation of apparatus embodying the invention;

FIG. 2 is a top plan view of the apparatus of FIG. 1;

FIG. 3 is a sectional view of a portion of the apparatus, taken along3-3 of FIG. 4;

FIG. 4 is a sectional view taken along 4-4 of FIG. 3;

FIG. 5 is a vertical sectional view of another portion of the apparatus;

FIG. 6 is a vertical sectional view of a pressure differential operatedswitch;

FIG. 7 is a diagrammatic plan of a fragment of a template; and

FIG. 8 is a block diagram of the logic circuitry.

Referring to the drawings, X-Y worktable 20 is mounted for left-to-rightindexing on rods 22 supported in carriage 24, and carriage 24 is in turnmounted on rods 26 supported on frame 28 to permit in-out indexing ofthe table.

For highly accurate in-out indexing, solenoid actuated 0.1 inch pitchrack 30 is fixed to carriage 24 to mate with rack 32 fixed to frame 28.Racks 34, 36, respectively fixed to table 20 and carriage 24, aresimilarly provided for left-right indexing.

Table-actuating hydraulic cylinder 40 is fixed to carriage 24 and hasits piston rod connected to table 20 through compliant coupling 42,which accommodates slight corrections in table movement upon the matingof racks 34 and 36. Similarly, carriage-actuating hydraulic cylinder 44is fixed to frame 28 and has its rod connected to carriage 24 throughcompliant coupling 46.

A tool unit 48 (e.g. a drill) is mounted above table 20.

Rectangular template support frame 50 is cantilevered at one side oftable 20, frame extension 52 being solidly bolted to the table. Mountedon frame 50 is master template 54, consisting of a steel plate throughwhich holes 56 (0.040 inch diameter on 0.1 inch centers) are drilled ina rectangular grid pattern with rows and columns (of, e.g., I00 holeseach) respectively Mounted in fixed position slightly below template 54,inside frame 50, is photoelectric cell 80 (FIGS. 1,

Fixed just above the template is a head 82 from which depends a hollowguide 84 (FIG. 5) around which fits a shell 86 (FIGS. 1, 3-5) biased byspring 88 against mask 70. Through the bottom wall 90 of shell 86 extendcentral light hole 92 which communicates with the hollow interior ofguide 84, and four air holes 94a-d spaced 90 apart on a circle coaxialwith hole 92. Each air hole 94ad communicates with a passage 96adthrough the wall of shell 86.

Light source 98 is positioned inside guide 84.

Air passages 96a-d are respectively connected through tubes 99a-d toorifices 100 (FIG. 6) of four normally open pressure differentialoperated switches 102ad (FIG. 1). Each switch l02ad is supplied with airat a fixed pressure (e.g. 2 p.s.i.g.) through orifice 104 on one side ofa flexible membrance 106, and is supplied with air at a slightly higherpressure (e.g. 3 p.s.i.g.) through orifice 108 and adjustable needlevalve 110 on the other side of membrane 106. Orifice 100 communicateswith the high pressure side of membrane 106.

Slots 72 are of the following forms (FIG. 7): slots 72a extend from ahole 56 in one direction perpendicular to the axis of current tablemovement, and are used to cause a turn of the table (as indicated by thearrows) without actuation of tool 48; slots 72b extend both sides of ahole 56 along the axis of current table movement and are used to causeactuation of tool 48 without a change of table direction; slots 72c areL-shaped, and extend from a hole 56 both in the trailing direction oftable movement and in the direction of a desired table turn, and areused to cause tool actuation and turn of the table. When no slots arepresent at a hole 56 (as hole 56a of FIG. 7), there will, of course, beno movement from that stop position without operator intervention (i.e.,an end of program stop occurs).

Switches l02a-d and photoelectric cell 80 are electrically connectedthrough logic circuitry to control the operation of hydraulic cylinders40 and 44, and to control the actuation of tool 48.

In operation, one of cylinders 40, 44 will be actuated to start tableand frame 50 in motion along the X or Y axis. Except where a slot 72appears mask 70 will block transmission of light to cell 80, and willseal holes 94a-d sufficiently to keep switches l02a-d open. When a slot72 and grid hole 56 become aligned with light hole 92 light passes fromsource 98 to cell 80 to stop the table, and one or two of air holes94a-d will be positioned over slot 72 so that the high pressure side(s)of the corresponding switch(es) 102a-d will be momentarily exhausted,closing the switch(es).

The heart of the logic circuitry is shown schematically in FIG. 7,conventional electrical and hydraulic components being used to carry outthe logical functions.

Upon receipt of a sufficiently intense signal from photocell 80,adjustable gating unit 120 provides an amplified signal to stop control122, which causes cylinders 40 and 44 to be locked in position, stoppingthe table. Racks 30 and 34 are closed against their mating racks,accurately aligningthe table, any error being taken up in the compliantcouplings. Considering the case in which slot 72 is of the form 72a, andin which the table had been moving in, e.g., the direction from hole 94ctoward 94a, either switch 10212 or 102d will be closede.g. 102b if aright turn is desired. In turn, direction control relay l24b will close.At the same time, memory causes direction control relay 124d-whichrepresents the trailing direction along the intended axis of tablemovement after the turn-to be latched in an open position. Gate relay126, upon receipt of signals from stop control 122 and switch 102b, inturn enables the closing of corresponding work cycle relay 128b. Theactuation of only a single work cycle relay prevents actuation of toolcontrol relay 130, so that tool 48 does not operate. Instead, timingunit 132, after a predetermined delay, interrupts the output of stopcontrol 122, causing rack 30 to open and cylinder 44 to be actuated fora right turn movement of the table. Memory 125 is cleared by unit 134,except that trailing direction relay 124d remains latched open.

In the event that the next slot 72 to align with hole 92 is of the form721;, the operation just described will vary in the following respects.Since two switches, 102d and 102b, will now be closed, two correspondingwork cycle relays, 128d and 128b, will close, causing work tool relay130, and hence tool 48, to be actuated. By appropriate circuitry,including a limit switch (not shown) operated by movement of tool 48,the output of timing unit 132 is delayed until the return of tool 48.Since relay 124d is still latched open, directional information to thecontrols for cylinders 40 and 44 will unambiguously signal continuedmovement in the direction of hole 94b.

When the aligned slot is of the form 720 operation is much the same,except that a turn is carried out and a new trailing direction closedrelay is latched open, the previously latched direction control relaybeing unlatched upon clearing of the memory.

Gating unit 120 is preferably set to provide an output when 50 percentof a hole 56 overlaps hole 92, to accommodate the time delay required tostop the table.

Pushbutton is provided to initially energize the system.

Other embodiments will occur to those skilled in the art and are withinthe following claims.

What is claimed is:

1. In apparatus comprising a worktable, a tool unit for carrying out awork cycle, an X drive unit for causing relative table-to-tool movementalong an X axis, and a Y drive unit for causing relative table-to-toolmovement along a Y axis perpendicular to said X axis, that improvementconsisting of indexing and cycling mechanism for controlling saidmovement and said cycle, comprising a template having first and secondphysical characteristics each varying along both said axes in accordancewith the desired pattern of said movement and said cycling,

a first sensor unit responsive to said first physical characteristic toprovide table stop signals,

a second sensor unit responsive to said second physical characteristicto provide table direction signals and work cycle signals and comprisingfour individual sensors respectively corresponding to the fourdirections along said axes,

said template and said sensor units being mounted to undergo relativesensor-to-template movement in precise correspondence to said relativetable-totool movement, and logic circuitry responsive to said sensorunits, to

cause said drive units to stop said relative movements in response to asaid table stop signal, to cause said tool unit to carry out said workcycle in response to a said work cycle signal, and to cause said driveunits to renew said relative movements in accordance with said tabledirection signals, said template having a plurality of first local areasin which said first physical characteristic has a difference from theremainder of said template which difference is detectable by said firstsensor unit and a plurality of second local areas, extending from saidfirst local areas in the respective directions of desired renewal ofsaid relative movements, in which said second physical characteristichas a difference from the remainder of said template which difference isdetectable by said second sensor unit, each said second local area beingarranged to align with a single individual sensor of said second sensorunit upon alignment of the corresponding first local area with saidfirst sensor unit, said logic circuitry being responsive to simultaneousalignment of a pair of said individual sensors with a pair of saidsecond local areas to cause said tool unit to carry out said work cycle.

2. The improvement of claim 1 wherein said first physical characteristiccomprises transmissivity of said template to light and said first sensorunit comprises a photosensitive device.

3. The improvement of claim 2 wherein said template comprises a platehaving a rectangular grid of uniformly spaced holes, and a program maskfor selectively optically exposing some of said spaced holes andcovering others thereof.

4. The improvement of claim 2 wherein said second physicalcharacteristic comprises transmissivity of said template to air and saidsecond sensor unit comprises a pressure sensitive device.

5. The improvement of claim 1 wherein said logic circuitry includes amemory responsive to a said individual sensor aligned with a said secondlocal area to prevent a said additional second local area adjacent asubsequent first local area with which said first sensor unit is alignedfrom effectively causing said individual sensor to provide a said tabledirection signal.

6. The improvement of claim 1 wherein said characteristics varydiscontinuously.

1. In apparatus comprising a worktable, a tool unit for carrying out awork cycle, an X drive unit for causing relative table-totool movementalong an X axis, and a Y drive unit for causing relative table-to-toolmovement along a Y axis perpendicular to said X axis, that improvementconsisting of indexing and cycling mechanism for controlling saidmovement and said cycle, comprising a template having first and secondphysical characteristics each varying along both said axes in accordancewith the desired pattern of said movement and said cycling, a firstsensor unit responsive to said first physical characteristic to providetable stop signals, a second sensor unit responsive to said secondphysical characteristic to provide table direction signals and workcycle signals and comprising four individual sensors respectivelycorresponding to the four directions along said axes, said template andsaid sensor units being mounted to undergo relative sensor-to-templatemovement in precise correspondence to said relative table-to-toolmovement, and logic circuitry responsive to said sensor units, to causesaid drive units to stop said relative movements in response to a saidtable stop signal, to cause said tool unit to carry out said work cyclein response to a said work cycle signal, and to cause said drive unitsto renew said relative movements in accordance with said table directionsignals, said template having a plurality of first local areas in whichsaid first physical characteristic has a difference from the remainderof said template which difference is detectable by said first sensorunit and a plurality of second local areas, extending from said firstlocal areas in the respective directions of desirEd renewal of saidrelative movements, in which said second physical characteristic has adifference from the remainder of said template which difference isdetectable by said second sensor unit, each said second local area beingarranged to align with a single individual sensor of said second sensorunit upon alignment of the corresponding first local area with saidfirst sensor unit, said logic circuitry being responsive to simultaneousalignment of a pair of said individual sensors with a pair of saidsecond local areas to cause said tool unit to carry out said work cycle.2. The improvement of claim 1 wherein said first physical characteristiccomprises transmissivity of said template to light and said first sensorunit comprises a photosensitive device.
 3. The improvement of claim 2wherein said template comprises a plate having a rectangular grid ofuniformly spaced holes, and a program mask for selectively opticallyexposing some of said spaced holes and covering others thereof.
 4. Theimprovement of claim 2 wherein said second physical characteristiccomprises transmissivity of said template to air and said second sensorunit comprises a pressure sensitive device.
 5. The improvement of claim1 wherein said logic circuitry includes a memory responsive to a saidindividual sensor aligned with a said second local area to prevent asaid additional second local area adjacent a subsequent first local areawith which said first sensor unit is aligned from effectively causingsaid individual sensor to provide a said table direction signal.
 6. Theimprovement of claim 1 wherein said characteristics varydiscontinuously.